Objective: To establish an interspecies somatic cell nuclear transfer (iSCNT) technique for deriving blastocysts having human chromosome complements without sacrificing human oocytes.
Design: Prospective, randomized study undertaken in vitro.
Setting: University-affiliated hospital and laboratory, Seoul National University.
Patient(s): Postpartum women with natural spontaneous vaginal delivery.
Intervention(s): Human cord fibroblasts were retrieved from five postpartum women from whom informed consent was obtained. After subculture and cryopreservation, serum-starved cells were transferred into enucleated bovine oocytes.
Main outcome measure(s): Embryo development, karyotype, and the presence of mitochondrial DNA (mtDNA).
Result(s): A total 1,742 oocytes were provided for iSCNT and results showed that both fibroblast batch and reconstruction method significantly affected iSCNT outcome. An iSCNT using a single DC pulse of 1.9-2.1 kV/cm for 20 microseconds yielded better rates of fusion (30%-56%) and cleavage (36%) than the other iSCNT protocols. Four to 9% interspecies embryos produced with the optimized method developed to morulae or blastocysts after cultured in a serum-free medium. Results from karyotyping demonstrated that 56% of interspecies embryos evaluated had human chromosome complements. In polymerase chain reaction (PCR) analysis of a single embryo, both human and bovine mtDNAs were detected until the 16-cell stage, whereas only the bovine mtDNA was found beyond the morula stage.
Conclusion(s): An iSCNT using human cord fibroblasts and bovine oocytes can yield blastocysts and the results of karyotyping and mtDNA analysis confirmed the feasibility of the iSCNT technique.